1. Field of the Invention
The present invention relates to a long member bending apparatus suitable to bend a long member such as a pipe member, bar member, shape member, and the like in a curved shape.
2. Description of the Related Art
There is conventionally a braid or lace bending apparatus disclosed in Japanese Examined Patent Application Publication No. Sho58-43165 (43165/83) as a bending apparatus for being a long member in a curved shape. The braid bending apparatus is used to form bent products such a window frame structure for automobile, and the like from strip materials having various cross sections. The braid bending apparatus is composed of a positioning guide having a plurality of rollers that form a gap therebetween to pass a material therethrough, a bending guide having a plurality of rollers that form a gap therebetween to pass the material supplied from the positioning guide therethrough, an outside frame for supporting the bending guide by a universal joint mechanism so as to incline the bending guide freely, a rotary plate mechanism for rotating the outside frame about the direction in which the material is supplied from the positioning guide as an axis, an X-Y slide mechanism on which the rotary plate mechanism is mounted so that the rotary plate mechanism is moved on a plane vertical to the direction in which the material is supplied from the positioning guide, and a computer for controlling. This bending apparatus has an advantage that it can correct twist distortion produced to a material having an asymmetric lateral cross section by applying twist to the material by the rotary plate mechanism. However, the apparatus has a problem in that it has a complicated structure because the bending guide is supported by the assembly of the respective movable elements of the outside frame, the rotary plate mechanism, and the X-Y slide mechanism and that the apparatus is increased in size because the bending reaction force of the material is transmitted from the bending guide to the respective elements of the outside frame, the rotary plate mechanism and the X-Y slide mechanism in series and thus all the elements must have strength and rigidity withstanding the bending reaction force of the material.
There is also a pushing pass bending apparatus disclosed in Japanese Examined Patent Application Publication No. Hei5-12047 (12047/93) as another bending apparatus. This pushing pass bending apparatus bends a pipe member, a shape member, and a solid member, and is composed of a guide cylinder through which a material is passed, a die through which the material supplied from the guide cylinder is passed, and a means for relatively offsetting the central axis of the guide cylinder from the central axis of the die. Further, Japanese Examined Patent Application Publication No. Hei7-110382 (110382/95) discloses an apparatus improving the pushing pass bending apparatus disclosed in Japanese Examined Patent Application Publication No. Hei5-12047 (12047/93). This improved type pushing pass bending apparatus is provided with an inclining mechanism for optionally or freely inclining the central axis of a die in a direction in which a material is bent and advanced by forming the outer peripheral side of the die in a spherical shape and disposing a bearing for receiving the spherical portion of the die, in addition to a mechanism for relatively offsetting the central axis of a guide cylinder from the central axis of a shape hole as in the conventional apparatus. The inclining mechanism makes it possible to bend a material with a bending radius smaller than a conventional one with sufficient accuracy. However, the pushing pass bending apparatus and the improved pushing pass bending apparatus have a problem in that they cannot twist a material and thus cannot bend a strip material while twisting it because the apparatuses do not rotate the die with respect to the central axis thereof.
As described above, the bending apparatus disclosed in Japanese Examined Patent Application Publication No. Sho58-43165 (43165/83) has the advantage that the twist distortion of a material having an asymmetric lateral cross section can be corrected by the rotary plate mechanism. However, the apparatus has a problem in that it has the complicated structure because the bending guide is composed of the series assembly of the respective movable elements of the outside frame, the rotary plate mechanism, and the X-Y slide mechanism and that the apparatus is increased in size because the bending reaction force of a material is transmitted from the bending guide to the respective elements of the outside frame, the rotary plate mechanism, and the X-Y slide mechanism in series and thus the respective elements must have strength and rigidity withstanding the bending reaction force of the material. Further, the respective pushing pass bending apparatuses disclosed in Japanese Examined Patent Application Publications Nos. Hei5-12047 (12047/93) and Hei7-110382 (110382/95) have a problem in that they cannot apply twist to a material because the die does not rotate with respect to the central axis thereof.
An object of the present invention is to solve the above problems and to provide an improved long member bending apparatus having a simple structure and high rigidity and capable of bending not only a pipe member, a bar member, and the like having a symmetrical lateral cross section but also a strip member that must be twisted.
To achieve the above mentioned object, a long member bending apparatus of the present invention includes a bending head for bending a long member in a curved shape; a material supply unit for supplying a long member to the bending head, and a control system for controlling the bending head and the material supply unit, wherein the bending head comprises a base plate having a guide pipe, through which a guide hole for passing the long member supplied from the material supplied therethrough is formed, standing upright at the center of a base plate; a movable plate having a die, which applies a bending force to the long member supplied from the guide pipe forward while passing it therethrough, disposed at the center thereof; and six extendable units comprising hydraulic cylinders interposed between the base plate and the movable plate and universal joints disposed to both the ends of each hydraulic cylinder, wherein the six extendable units join the universal joints to the peripheral edge portions of both the base plate and the movable plate so as to be formed in an approximate truss state and construct a parallel link mechanism for causing the movable plate to execute a motion having three degrees of freedom of translational movement and three degrees of rotation with respect to xyz coordinates set on the base plate by expanding and contracting the hydraulic cylinders. The control system adjusts the lengths of the respective hydraulic cylinders by setting the position and inclination of the movable plate with respect to the base plate and the twist angle of the movable plate about the central axis thereof.
When the long member is bent by the long member bending apparatus arranged as described above, the long member is inserted into the die of the movable plate from the guide hole of the base plate until the tip end of the long member reaches the die, and the bending parameters comprising the offset (a) of the central point of the die with respect to the axial center of the guide hole, the distance (b) from the tip end of the guide pipe to the central point of the die along the axial center of the guide hole, the inclining angle (xcex1) of the plane including lateral cross section of the die with respect to the plane including lateral cross section of the guide hole, and the twist angle (xcex8) of the movable plate about the axial center of the die are set by the control system according to a desired bending radius (xcfx81) of the long member. The material supply unit pushes the long member to the bending head in a state that the control system sets the bending head by expanding and contracting the six extendable units according to these bending parameters. Thus, the long member is bent to the bending radius (xcfx81) between the guide hole and the die in such a manner that the outer peripheral surface thereof is restricted at the two positions of the guide hole and the die as well as the long member is processed to the twist angle (xcex8) by the die.
The bending head has a simple structure because it is composed of the base plate, the movable plate, and the six extendable units connecting both the plates as well as the movable plate is restrict with high rigidity because it is supported by the six extendable units fixed to the peripheral edge portion thereof. According to the bending head, a long member such as a pipe, bar, and the like having a symmetrical cross section can be bent by setting the three parameters of the offset (a) of the central point of the die with respect to the axial center of the guide hole, the distance (b) from the tip end of the guide pipe to the axial center of the guide hole, and the inclining angle (xcex1) of the die with respect to a plane perpendicular to the axial center of the guide hole. Further, a strip member that must be twisted when it is bent can be processed by further adding the parameter of the rotational angle (xcex8) of the movable plate about the axial center of the shape hole, in addition to the above three parameters.